Dental handpiece



Jan. 12, 1965 c. A. ELLIS 3,164,903

DENTAL HANDPIECE Filed April '7, 1960 INVENTOR.

CHARLES A. ELLIS to a location remote from the work area.

United States Patent 3,164,993 DENTAL HANDPEEQE Charles A. Ellis, Point Road, Box 145, Marion, Mass. Filed Apr. 7, 1960, Ser. No. 20,775 8 Claims. (till. 32-27) This invention relates to dental apparatus and more particularly to air powered dental tool driving devices or handpieces as they are called. The subject invention is further limited to air driven handpieces which impart a longitudinal motion to the tool as distinguished from those which drive the tools with a continuous rotary mo tion. The invention is further limited to handpieces having a reciprocating tool driven by the vibratory motion of a free piston typeof device such as shown in my copending application, Serial Number 800,717; wherein motion of the tool is due to the reactive effect of the free piston and not to a direct coupling between the tool and the driving piston.

The primary purpose of this handpiece is for dental cleaning and polishing operations. Conventional rotary tools have inherent disadvantages in that it is not possible with such tools to polish in the direction along the tooth axis in the direction of the natural imperfections of surface. They are further handicapped in approaching the gum line and are very likely to abraid the gums in the process of polishing. Previously available reciprocating tools were likewise handicapped. With the tool directly coupled to the piston it is very easy to stall the tool by pressure against the work unless the power of the device is considerably greater than that required for the cleaning and polishing operations alone. Control of such an over powered tool was therefore difficult. By retaining the desirable reciprocating motion but isolating the piston from the tool a new kind of handpiece results. It is no longer possible to stall the motor by any degree of pressure against the work surface. This permits a reduction of total power to that required for the cleaning and polishing operations and nominal frictional losses. Such a small amount of power is thus required that it is possible with this device to approach the gingival line without danger and to even push the gum back with the tool, wholly without danger of abraiding or causing bleeding of the gums.

Improvements which the subject invention has over my copending application, Serial No. 800,717, are likewise of importance. The former device was occasionally subject to failure to start on what might be termed a dead center condition when the piston had stopped in a position so as to completely out off air from the incoming supply line. This has been overcome in a manner described in detail in the specification. The former device exhausted the air or other fluid from the power stroke directly into the oral cavity in common with other dental devices presently available. The improved handpiece has a completely sealed system, wherein the compressed air for driving is conducted through the handle to the free piston motor and the entire exhaust is then conducted back through the handle and a suitable conducting tube Two very considerable benefits result. The noise of the motor is largely caused by the intermittent release of pulses of high pressure air. By conducting the exhaust away no annoying resonance in the oral cavity is experienced. It is also possible to vent the exhaust to a suitable mufliing device and nearly eliminate the sound even at the point of exhaust. The second benefit is that in such a sealed system neither doctor not patient need be concerned with the makeup of the compressed air or other fluid. Without the sealed system concern would be justified as to the purity of the intake of, for example, a cellar located compressor. Again the sealed system makes possible the use ice of any type of lubricant without concern as to its effect upon the respiratory system of either doctor or patient. A further improvement of the subject device is a greatly simplified piston and cylinder construction resulting in greater ease of manufacture and economy as well as permitting a considerable reduction in size which is of importance in a device which must be used within the human mouth. Still another improvement in this device is the method of resiliently mounting the power head to permit its vibration without forcing the entire handle to follow the motion. The resilient exhaust tube surrounding the air inlet conductor provides a comfortable and secure finger contacting area for guiding the instrument in use.

Accordingly, a primary object of this invention is to provide a simplified driving mechanism for dental handpieces of the free piston type.

Another object is to provide in such a mechanism for reliable self starting operation.

Another object is to provide a sealed air system in the handpiece and means for conducting the exhaust to a location remote from the handpiece.

Still another object is to provide a means of securely and reliably holding removable abraiding tools in the handpiece in spite of the considerable vibration to which they are subject in use.

Other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings and it will be apparent that many changes may be made in the details of construction and arrangement of parts shown and described without departing from the spirit of the invention as expressed in the accompanying claims. I, therefore, do not wish to be limited to the exact details of the construction and arrangement of parts shown and described as the preferred form only is given by way of illustration.

Referring to the drawings:

FIG. 1 is a side elevational view in partial section of a handpiece of the type covered by this invention;

FIG. 2 is an enlargedside sectional view of the head end of the handpiece of FIG. 1;

FIG. 3 is a side elevational View in partial section of a metal and plastic tool adapted for use in the handpiece of FIG. 1;

FIG. 4 is a side elevational View of an all plastic tool adapted for use in the handpiece of FIG. 1;

FIG. 5 is an end view of FIG. 3 taken in the direction of the arrows 5-5;

FIG. 6 is an end view of FIG. 4 taken in the direction of the arrows 6-6.

Referring to FIG. 1, there is shown a dental handpiece which incorporates the invention. This handpiece is of the air-powered free piston type and comprises a tubular handle section designated generally by the numeral 11, at the forward end of which is mounted, in a manner to be described, a power head designated generally by the numeral 12. A polishing tool, designated generally by numeral 13, may be securely but removably mounted in the head 12 as will be explained hereinafter. Passing through the bore of the tubular handle are two concentric resilient plastic conducting tubes; the inner tube 14 for incoming air and the outer tube 15 for exhaust air. The bore of the handle is flared as shown at 18 adjacent the large end of the handle to prevent cutting of the plastic tube 15 while the handpiece is in use. A constriction 16, within the handle 11, frictionally secures it to the outside of tube 15 in a manner which permits adjustment of its position relative to head 12. Tubes 14 and 15 are connected respectively to a compressed air supply and a suitable mufiler of conventional construction (not shown).

Details of the head construction are most clearly shown in the sectional view FIG. 2. The head 12 comprises a self-starting free piston air motor, means for mounting the motor with a handle and means for attaching a suitable tool to the head for imparting to the tool a reciprocating vibratory motion. The air motor is comprised of a cylinder 19, cylinder caps 23 and 24 and piston designated generally by numeral 25. The piston is of stepped form with a major diameter 26 hearing in sliding relationship upon the inner surface of the cylinder 19; its minor diameter 27, slides upon the inner surface of ring 20, the latter being securely pressed into place internally of cylinder 19 and having a distinct chamfer 21 on the face adjacent the large piston diameter. Both sliding fits are made with minimum clearance to prevent leakage of air along the piston surfaces. Piston 25 is further provided with a concentric axial bore 28 which starts at the end of major diameter but does not penetrate through the minor diameter end of the piston. A slot 29 is cut through the minor diameter wall at right angles to the piston axis so as to intersect the bore 28 adjacent its inner terminus to complete an air passage through the piston. Three equally spaced grooves 3d are cut into the inner surface of the cylinder wall and parallel to the cylinder axis in the section traversed by the major diameter section of piston, also for the purpose of forming air passages. These grooves must be slightly longer than the length of the major diameter section of piston and must start adjacent the cap 24. The cylinder wall is perforated at 31 adjacent the ring 20 and in the opening is fixed in pressure tight relationship, a metallic inlet air conductor 32. The cylinder wall is also perforated at 33 on the opposite end of ring 20 to form an exhaust passage from within the cylinder to the inside of exhaust manifold 22. Manifold 22 is firmly fixed in pressure tight relationship to the wall of cylinder 19. The outer end of the manifold 34 is of cylindrical form. The inlet air conductor 32 passes through the manifold and is firmly attached to it along one side of the cylindrical section 34. The outer end of conductor 32 extends to a point 17, within the handle 11, at which point the flexible plastic air supply line 14 is stretched over it to form a pressure tight coupling. The larger diameter plastic exhaust tubing 15 is passed over tube 14 and conductor 32 and stretched over the cylindrical portion 34 of the manifold also in a pressure tight manner.

In FIG. 3 is clearly shown the construction of a typical metal and plastic tool adapted for use in the handpiece for chipping and cleaning operations. The metal body of the tool is generally D shaped as shown in section in FIG. 5. The large cylindrical surface is grooved as shown to form a series of sharp edges 39 adapted for scraping. The base is beveled away from the plane surface 38 to form a straight chisel edge 44). The smaller diameter or tang 37 of the tool is grooved to form a number of holding edges 42. A sleeve 41 of resilient material, such as a polyamide, carrying screw threads 36 on its outer surface is pressed upon tang 37 and the edges 42 firmly prevent its withdrawal. In use the threads of the tool are engaged with those at 34 on the reduced end 35 of cylinder cap 23. The lubricity and elasticity of the polyamide material permits engagement of the threads with a slight interference fit without danger of abraiding either threaded body. Once seated the tools are secure against vibration because of the closeness of fit maintained by the elastic character of the polyamide material. They are easily removed by unscrewing when changing tools is desired. The sleeve 41 may be prevented from rotating upon tang 37 by cementing or by notches (not shown) in the holding edges 42.

FIG. 4 shows a typical all plastic tool adapted for use in this handpiece for polishing operations. It is provided with screw threads 36 on its tang portion. The surfaces are arranged as shown in FIG. 6 to provide for polishing concave, flat or convex tooth surfaces and with sharp edges for reaching surfaces between teeth.

Again polyamide resin is the preferred material for these tools. Not only is it most effective for the screw M coupling but its resilience and high degree of toughness make it particularly adapted for use with the abrasive materials used in polishing teeth. It carries abrasive well yet does not itself wear away rapidly so many surfaces may be polished before a change of tool shape takes place.

In operation the air motor is supplied with high pressure air through tube 14 and inlet air conductor 32. This air passes into the closed annular space 43 between the ring 20 and the step 44 of the piston 25. Since the piston is free to move it is displaced upwardly toward cylinder cap 24. When the piston step 44 reaches the lower end of the grooves 30 air can escape past the piston into space 45. Shortly thereafter the upward thrust due to the air pressure acting upon the area of the piston step 44 is overcome by a downward force due to air pressure acting upon the total piston head area since slot 29 is sealed by ring 20. The preferred ratio of the head area to the step area has been found to be 2:1. As soon as the net downward thrust has produced motion to place step 44 opposite the lower end of grooves 30 the air supply to the head is cut off and further motion is due to expansion of the trapped air and to the inertial effect of the piston. This motion carries the piston downward until the lower edge of slot 29 clears the bottom of ring 20. At this point remaining air in the head end may escape, the inertia effect aiding in keeping 29 clear of ring 20 for a short period of time, thus opening the route from space 4-5 through. bore 28 and slot 29 into exhaust space as and from there through port 33 into the exhaust manifold 22 and on out through exhaust tube 15. As soon as the pressure in 45 has been sufficiently relieved the thrust upon step 4 from the incoming pressurized air assumes control and causes upward motion once more. This seqence is repeated at a rate dependent upon the mass of the piston, the air supply pressure and the relationship between the ring, piston and air passages. In working with this device it has been found that a frequency of about 250 cycles per second, which is easily obtained, is very effective in performing the intended work. An annular chamfer 21, on ring 26 is an important factor in providing for selfstarting. Without this the piston, when down against the ring, effectively seals the entrance port but with it air will always bleed into the space 43 to initiate action. The parts must be so proportioned that with the piston at the other extreme air may pass through slot 29 to initiate motion.

The piston, being completely sealed within the unit is not subject to stalling due to overload since no load can be directly applied to it. In its rapid reciprocating motion it does, however, set up a vibratory reaction of the entire head and of course of the tool which is mounted in the head. In order to partially isolate this vibration of the head from the handle the resilient plastic tube 15 is used as a loose coupling between these members.

The tube 15 serves also as the contact area for the fingers of the operator and as such gives a firm and positive control of the head without transmitting more than a tolerable portion of the vibration to the fingers. Inlet conductor 32, by extending within the handle 11, lends stability to the head but since all contact points are to resilient plastic material it is effectively decoupled and likewise transmits little to the handle.

In the above description the air supply has been referred to as pressurized. This terminology is to be taken in the relative sense since the air motor of this device works equally well with a negative pressure in the exhaust and air at atmospheric pressure as inlet air.

As a dental instrument this device serves as a chipping tool and as a cleaning and polishing tool. I have found that the rapid vibratory motion imparted to the tool is very effective in calculus removal. With the chisel edge of a metallic tool such as shown in FIG. 3 and only moderate finger pressure holding the device against the tooth, large scales or calculus are separated at a time.

In more persistant deposits the chips are of smaller' is somewhat less than with the manual tool'for the like result. In thin deposits the multifluted surface has a file like effect and quickly reduces the relatively soft deposits without any deleteriouseffect upon the tooth structure. Change from a metallic tool to a plastic one either with an abrasive slurry or with abrasive incorporated in the tool adaptsthe instrument for polishing operations. The tools can take many forms, that shown in FIG. 4 being illustrative of one having multiple functions. The surfaces and edges are well adapted for holding the abrasive against the tooth surfaces while the vibratory motion carries out the polishing action desired.

From the foregoing description it will be seen that a simple, efiicient and economical means is provided for accomplishing all of the objects and advantages of this invention.

I claim: t

1. A dental apparatus comprising a sealed power head flexibly mounted upon a tubular handle, including a tool holding device integral with said head, an air driven free-piston motor device within said power head by means of which a reactive vibratory motion is imparted to said head and to the tool holding means mounted upon it, said piston having'no metallic driving connection with said tool holding means, a sealed air supply conductor passing through said handle for connection to a supply of compressed air for driving said motor and a sealed flexible and resilient exhaust conductor surrounding said air supply conductor and passing through said handle for the dual purpose of carrying exhaust air from said motor to a point remote therefrom and to provide a resilient mounting for the power'head, the said tubular handle member frictionally mounted upon said resilient exhaust conductor and slideable longitudinally thereof whereby the flexibility of coupling between the handle and the power head may be changed to modify the vibration of said power head.

2. A dental apparatus of the character described comprising atubular handle member, frictionally mounted upon the outside of a flexible air conductor, in loose cou pled relationship with said handle a sealed air driven power head comprising a free piston motor together with a sealed air supply conductor for attachment to a source of compressed air whereby said piston may be caused to vibrate longitudinally of said head, sealed exhaust means leading to a point remote from said handle and tool holding means mounted axially at one end of said head adapted for holding a tool for chipping, cleaning or polishing teeth when said headis caused to vibrate longitudinally by the reactive forces of the piston vibration, said tubular handle lement adjustable longitudinally of said flexible air conductor toward and away from said head whereby the amplitude of vibration of the head may be modified in accordance with the Work to be performed there being no continuous metallic driving connection between said piston and said tool holding means.

3. An air operated instrument of the character described comprising a tubular handle member frictionally mounted upon a flexible and resilient air exhaust tube, a

tion to said head and to the tool holding means mounted therein, said tubular handle element adjustable along said air exhaust tube toward and away from said power head to permit adjustment of the amplitude of vibration of said head'and hence of the tool fiexdly mounted thereon.

4. An air operated dental chipping, cleaning and polishing apparatus comprising a sealed self-starting free piston motor device mounted to vibrate longitudinally of a tool holding power head to cause reactive longitudinal motion thereof, tool holding means integral with and axially located at one end of said head, a flexible and resilient exhaust air tube sealed to the exhaust manifold of said motor and passing through a tubular handle element and thence to a remote muflling device, said tubular handle element frictionally mounted upon said exhaust air tube and adapted for adjustment along said tube toward and away from said power head whereby the amplitude of vibration of said head may be altered, a stiff metallic air supply conductor sealed to the inlet port of said motor and passing within the manifold and exhaust air tube to a point within said handle, said resilient exhaust tube and said stiff metallic air supply conductor cooperating to permit a limited radial motion of said power head about a point located within said tubular handle, a

flexible air supply tube sealed to the terminal end of said conductor and extending within said exhaust air tube at least to a point remote from said handle for connection to a source of compressed air by means of which said free piston motor is caused to vibrate, and to reactively drive power head mounted in sealed relationship at one end of said exhaust tube, from said head and sealed thereto and within said exhaust tube a metallic air supply conductor extending into said tubular handle, sealed to said conductor a flexible air supply'tube also within said exhaust tube at least for a distance remote from said handle for connection to a source of compressed air, tool holding means integral with and mounted axially of said power head and at one end thereof adapted to hold dental tools for chipping, cleaning and polishing operations when caused to move longitudinally, a free piston air driven motor within said power head arranged to vibrate along the axis thereof and to impart by reaction a similar vibrathe power head and the tool holding means thereon whereby the above mentioned operations may be performed.

5. An air operated dental chipping, cleaning and polishing device comprising a free piston motor Within a sealed tool holding power head having sealed air supply conductor and sealed exhaust means passing through a tubular handle element, s'aid supply conductor and exhaust means cooperating to permit a limited radial motion of said power head about a point within said tubular handle, said motor including a stepped pistonwith axial air pas sage beginning at the larger diameter end thereof and terminating in communications with a slot adjacent the smaller diameter end and perpendicular to the piston axis, said piston sliding axially within a two diametered cylinder having air conducting grooves cut into its inner wall parallel to its axis adjacent the larger end thereof which acting in conjunction with the piston step determine the inlet event, a ring pressed into the opposite end of said cylinder to form the small cylinder diameter and serve as a bearing for the smaller piston diameter the outer end of saidring acting in conjunction with the piston cross slot to determine the exhaust event, its inner end chamfered on the outer diameter to assure an air passage to the bottom of the piston step even when the step is against the ring to. assure selfstarting operation, tool holding means axially mounted upon one end of said head by threads or other suitable means in fixed axial relationship integral with said power head which is caused to move with the head as the latter is forced into reactive vibration by the motion of the piston when said air supply conductor is connected to a source of compressed air whereby the tool may be used to perform its intended purpose.

6. An air driven dental handpiece for chipping, cleaning or polishing teeth comprising a free piston motor within a sealed tool holding power head, said motor including a stepped piston with axial air passage beginning at the larger diameter end thereof and terminating in communication with a slot adjacent the smaller diameter end and perpendicular to the piston axis, said' piston sliding axially within a two diametered ported cylinder having air conducting grooves cut into its inner wall parallel to its axis adjacent the larger end thereof which acting in conjunction with the piston step determine the inlet event, a ring pressed into the opposite end of said cylinder the bore of said ring forming the small cylinder diameter and serving as a bearing for the smaller piston diameter with the outer end of said ring acting in conjunction with the piston cross slot to determine the exhaust event, a chamfer on the outer diameter of the inner end of said ring to assure an air passage from inlet port to the bottom of said piston step even when the piston is in close conjunction with the inner end of said ring, to assure selfstarting operation of said piston a metallic air supply conductor sealed at one end to the inlet port of said cylinder and extending into a tubular handle, said metallic conductor serving the dual purpose of air pipe and as a radius arm for limited motion of the power head about a point within the tubular handle, an exhaust manifold sealed to the side wall of said cylinder and surrounding said air supply conductor and in communication with the cylinder exhaust port the outer end of said manifold being cylindrical in form, a flexible resilient exhaust tube sealed at one end to the cylindrical portion of said manifold and passing through the tubular handle in frictionalengagement therewith whereby said handle may be adjusted longitudinally of said exhaust tube to change the coupling between the handle and the head, said exhaust tube terminating at a distance from said handle, a flexible and resilient inlet air tube Within the bore of the exhaust tube sealed at one end to the air supply conductor within said handle and adapted for connection at its opposite end to a compressed air supply whereby said motor may be caused to vibrate longitudinally of said power head inducing in said head and to the hool holder mounted thereon a reactive longitudinal vibration suitable for performing the intended work.

7. A sealed dental apparatus comprising in combination a sealed power head, tool holding means at one end of said head adapted for holding edged or abrasive tools, an air driven free-piston motor device within said power head by means of which a reactive vibratory motion is imparted to said head and the tool holding means incorpo- 8 rated in it, a metallic air supply conductor connected to said motor at one end and to a flexible air conductor at the other end for connection with a supply of compressed air for driving said motor, a flexible exhaust conductor surrounding said metallic conductor connected to said head at one end and passing to a point remote from the termination of the metallic air supply conductor whereby the exhaust pressure pulses of said motor may be rnuffied before being exhausted to the surrounding air, a tubular handle element frictionally coupled to the flexible exhaust conductor adjacent the power head slideably adjustable toward and away from said head whereby the vibratory motion of said head may be changed in amplitude in accordance with the type of work to be performed.

8. A dental apparatus comprising a sealed power head including fixed tool holding means integral therewith, an air driven free piston motor device of the character described within said power head by means of which a reactive vibratory motion is imparted to said head and to the tool holding means mounted upon it, flexible inlet and exhaust air conductors sealed to said head, a tubular handle frictionally mounted upon said air conductors slideable toward and away from said head whereby the amplitude of vibration of said head may be adjusted.

References Cited in the file of this patent UNITED STATES PATENTS 443,691 West Dec. 30, 1890 1,046,560 Coulson Dec. 10, 1912 2,536,595 Dittmann Jan. 2, 1951 2,735,181 Carpenter Feb. 21, 1956 2,787,251 Becker Apr. 2, 1957 2,855,673 Gruenwald Oct. 14, 1958 2,937,444 Kern May 24, 1960 FOREIGN PATENTS 163,217 Austria June 10, 1949 

1. A DENTAL APPARATUS COMPRISING A SEALED POWER HEAD FLEXIBLY MOUNTED UPON A TUBULAR HANDLE, INCLUDING A TOOL HOLDING DEVICE INTEGRAL WITH SAID HEAD, AN AIR DRIVEN FREE-PISTON MOTOR DEVICE WITHIN SAID POWER HEAD BY MEANS OF WHICH A REACTIVE VIBRATORY MOTION IS IMPARTED TO SAID HEAD AND TO THE TOOL HOLDING MEANS MOUNTED UPON IT, SAID PISTON HAVING NO METALLIC DRIVING CONNECTION WITH SAID TOOL HOLDING MEANS, A SEALED AIR SUPPLY CONDUCTOR PASSING THROUGH SAID HANDLE FOR CONNECTION TO A SUPPLY OF COMPRESSED AIR FOR DRIVING SAID MOTOR AND A SEALED FLEXIBLE AND RESILIENT EXHAUST CONDUCTOR SURROUNDING SAID 